This paper reviews the general topic of fuel deterioration. Primary emphasis is on diesel fuels used in compression ignition engines, which power the majority of Army tactical and combat vehicles. Field problems regarding the fuel stability and related problems are summarized, and the status of on-going research and development programs is outlined. This information places in perspective the background which has prompted current research activities to detect, predict, and prevent fuel stability-associated equipment failures. Concern for anticipating deleterious product formation in current and future fuel formulations composed of diverse petroleum crude and synthetic (shale or coal) crude oils, fuel/equipment interactions, diverse storage conditions, and the increased desire for prolonged storage periods provides the driving factors in defining the Army's fuel stability research programs. While placing these concerns in perspective, the Army's present and future needs for diesel fuel stability and cleanliness control are identified.